Tire tread



Aug. 30 l TIRE TREAD Filed Jan. 19, 1951 miba- EEENP Hzgh w 5f /ff M??? United States Patent Goodrich Company, New York, N. Y., a corporation of New York Application January 19, 1951, Serial No. 206,880

2 Claims. (Cl. 152-209) This invention relates to tire treads and has for an object to provide a tread that combines to a high degree the qualities of resistance to skidding, resistance to wear and quietness in operation. v

It is especially desirable that tires for passenger automobiles have these three qualities to a high degree in the same tread construction. To have the desired wear resistance a tire should wear evenly andl retain the tread after many miles of service and to have the desired resistance to skidding the tire should grip effectively wet as well as dry pavements. Quietness of operation should be provided at all speeds of operation of the automobile. These qualities of tires have becomeof increased importance with the introduction of improved smoother pavements, and of vehicles having greater braking power and greater acceleration with quieter engines.

While tire treads proposed heretofore often have provided to some extent one or two of these qualities it has been diicult to provide all three qualities to-ahigh degree in a single tire. For instance, tire treads which have good skid resistance frequently have one or more of the following objectionable characteristics: noisy operation `lateral instability, inferior wear resistance and irregular wearing over the surface of the tire tread. Likewise tire treads which have been designed for long life and quiet operation frequently have lacked the desired skid-resistance.

It has been proposed heretofore, to the end of preserving maximum tread contact area while improving the;y skid resistance, to provide a series of spaced-apart incisions crosswise of the tread. While this has given-improved skid resistance the prior schemes have resulted in noisy operation which is exceedingly objectionable at times. The prior eiorts of which I am aware have all concerned themselves with what may be termed coarse spacing of the incisions, that is, spacing in the circumferential direction. of the tread for the most part not closer than about ten cuts per inch and in some cases as far apart as one incision every few inches. Tireswith cuts at coarse spacing have been found' to be exceedingly noisy in operation and have required expedients such as varying the `spacing ofthe incisions in an attempt to modify the sound waves causing the noise. v

As a result of numerous tests and experiments I have found that instead of resorting to coarse spacing, it is entirely feasible and moreover productive of vstrikingly improved results to utilize incisions across 'the tire tread of ne spacing in the longitudinal direction of the tread of more than 12 incisions per inch measured circumferentially of the tire and preferably considerably higher than this iigure, the incisions being cut substantially without the removal. of' tire material. Good results have been obtained withy ne spacing ofl about 16 incisions per inch although in some respects even better results are obtained with even liner spacing.

I have found as one of the results that the wear resistance. of tires with line spacing ofthe incisions is greatly improved over tires without the fine spacing, lt is, believed that the increased wear resistance obtained is attributable lit 2,716,435 Patented' Aug. 30, 1955 at least in part to the decreased relative movement between the tire tread surface and the road surface resulting from the increased number` of elements of tread material formed by the incisions, which elements in the case of the cuts at line spacing are bound together at one edge in a manner that may be likened somewhat to the leaves of a book. The leaves are mutually supported and at the same time are flexible for decreasing sliding movement of the leaf edges on the road and for yielding under blows by hard objects so as to lessen wearing by abrasion at the point of application of the force. The finely spaced incisions also decrease the resistance to bending of the tire tread which lesser bending resistance reduces the heat generated by hysteresis in operation and vthereby increases the wear resistance of the tread. It has been found that line spacing of the incisions increases skid resistance due to the multiplicity of leaf edges at the incisions which are available in the pavement contacting area to engage the pavement for wiping and gripping thel pavement. The incisions and thin leaves provide a multiplicity of closely spaced channels when the incisions, which are made without the removal of any material and are normally closed are opened by the action of the tread on the pavement. These channels are effective for'conducing water away from the gripping surfaces, which is also an important factor in increasing the skid resistance. ln addition l have discovered that exceedingly quiet operation is `obtained with tire treads having tine spacing even though no variable spacing is used and the close incisions are uniformly spaced- It is an objectv of this invention to provide to a high degree in the same tirel tread the combined qualities. of

resistance to wear, uniformity of wear, resistance to skidding, quietness and stability.

Other objects are to provide improved flexibility and*v yieldability of the ti'rey tread, to provide a multiplicity of wiping and gripping' edges, andto provide a large tready surface area. A further object is toy provide a tread that maintains an attractive appearance evenafter extensivev service.

These and other objects willl be .apparent from thel following description, reference beingmadeto the accompanying. drawings in which;

Fig. l is. an elevation of a tire built in accordance withV interveningsidewalls- 1'3, 13. Reinforcingfplies 14, 141.

of woven or weftfless fabric may be embedded in the tire and extend from bead portion to bead portion andunder4 the tread '12..l Certain of the plies. 1.4, 14 may terminate short of the lbet-idportitms 11, '11 to provideabreakerply 15 at the crown of the tire 10. The roadengaging surface of the tread 12 has` circumferentialy grooves 16, -16 leaving circumferential laterally spacedapart ribs 17 17, although if desired other tread patterns may be used, or the ytread face may be pla-in all over.

In .accordance with the- .invention lthere is provided in the tread 12 a multiplicity of thin leaves 18, 18 formed by incisions19., 19 crosswise of the tread of fine spacing the circumferential` direction of the treadwhich incisions are made substantially without' the removal of tread inaterial. The incisions 19,., 1.9.- extend across theV tread 12. in a direction normalv to the centerline of the tread al.- though if desiredthe cuts may be somewhat oblique te the; centerline;

The objects of the invention of obtaining to a high degree the results of resistance to skidding, resistance to Wear and quietness in operation, are obtained with fine spacing of about 16 to 18 incisions per inch. Some of the advantages are obtained with less fine spacing than this, but to avoid objectionable noise problems and to obtain other advantages to a satisfactory extent I have found it desirable to use a spacing of more than l2 incisions per inch. The new results are found to be greater as the neness of the spacing of the incisions 19, 19 is increased considerably above l2 per inch, and tires with incisions at the exceedingly ne spacing of 26 per inch have exhibited excellent results.

While I prefer to use a depth of the incisions 19, 19 of somewhat more than half the height of the ribs 17, 17 to provide a high degree of flexibility of the leaves 18, 18, consistent with stability of the tread, the depth of the incisions may be decreased or increased from this amount while still obtaining many of the advantages herein described. It is preferred that the ratio of the width of the ribs 17, 17 to the height of the ribs be in a range where the ribs have adequate lateral stability despite the increased yieldability of the ribs resulting from the incisions at fine spacing. Excellent results have been obtained with ribs 17, 17 each of a width greater than the height of the rib and also with ribs of a width about the same as the height. I prefer that the Width of each rib be not less than about two-thirds of the height of the rib so as to accommodate the fine spacing I desire for the incisions and the advantages thereof without objectionably lessening the lateral stability of the ribs.

The human ear is capable of hearing sounds only within a limited range of frequencies, sometimes referred to as the audible range. In this range sounds of certain frequencies are more readily heard than those of other frequencies when they are produced at the same intensity. Therefore a tread-produced noise which is classed as being objectionable must have a frequency and an adequate intensity such as to be in the range where the human ear can distinguish the sound. In other words the sound must be over the threshold of audibility and below the upper limit of the audible range of frequencies to be classed as objectionable.

With tire treads having coarse spacing of the incisions the frequencies of the impulses produced at normal drivrange of frequencies which the human ear has difficulty in hearing or cannot hear.

The intensity of sound produced by tire treads has been observed to increase at a high rate with an increase in speed. With a tire constructed as herein described, the intensity at low speeds is of such a small magnitude that although the frequencies of the sound impulses produced at low speeds may be in the audible range the sound produced by the tire tread is not objectionable. I have found also that before the intensity of the sound impulses builds up by virtue of increase in speed to a point Where it might be objectionable to the ear the frequency of the sound impulses increases sufiiciently to pass out of the audible range of sound frequencies by virtue of the fine spacing of theincisions 19, 19.

Tires with ine spacing of the incisions have shown greatly increased life as determined by measurements of tread depth at various mileages over similar tires without the incisions in the tread. While all the reasons for the increase in the resistance to wear may not be at once apparent an important factor appears to be the exibility of the tread provided by the thin leaves 18, 18 between the incisions 19, 19. The exibility provided by the thin leaves 18, 18, permits resilient adjustment of the tread not with rough particles on ground surfaces, but also in the matter of reducing scuing as a result of the different rolling circumferences existing because of crowning of the tread. The ne spacing of the incisions as herein described provides leaves 18, 18 of the tread material of such thinness that a high degree of exibility is present for attainment of this result of greatly reduced Wear.

Because the exibility of the tread 12 is increased by the finely spaced incisions 19, 19 the heat which is produced in the tire 10 as it is tiexed in operation is dccreased. The work which is done in the tire tread 12 is less because the tread is cut by many incisions and the resistance to bending is lower. Therefore since less work is done in the tire the heat of hysteresis is reduced and the effect of heat in reducing the life of the tire is lessened. The multiplicity of incisions 19, 19 and thin leaves 18, 18 provide a multiplicity of edges at the tread contact surface. The edges operate to wipe the pavement surface and thus increase the skid resistance. In addition channels are formed when the incisions 19, 19 are opened upon contact with the supporting surface. The channels which result in operation are finely spaced and improve the skid resistance of the tread on Wet pavement by carry-1 Also the iiexiing the water away from the tread surface. bility of the tread surface increases the skid resistance because the ability of the tread to conform to the supporting ground surface is increased and the ground contacting area` of the tread is increased.

Variations may be made without departing from the scope of the invention as it is defined in the following claims.

I claim:

tread face a multiplicity of thin leaves extending transp versely of the tread and entirely across said traction elements with incisions between the leaves cut across the tread substantially Without the removal of tread material at substantially uniform fine spacing of about 16 incisions per inch measured circumferentially of the tread providing a high degree of skid resistance on Wet pavements by virtue of the multiplicity of flexible transverse leaf edges at the incisions, a high resistance to wear by virtue of the soft yieldability of the tread afforded by the fine spacing of the incisions and providing quietness of operation as a result of the low audibilty of the sound impulses produced by the multiplicity of leaves in the tread at all speeds of operation.

2. A resilient tire tread for resistance to slippage in the *direction of travel and for stability transversely to the direction of travel, said tread comprising a body of resilient rubber-like material including a plurality of circumferentially extending axially spaced traction elements, said 1elements having a multiplicity of thin leaves with incistantially uniform spacing of about 16 to 18 incisions per inch providing a high degree of skid resistance on wet surfaces by virtue of the multiplicity of flexible leaf edges and incisions and a high resistance to wear by virtue of the soft yieldability of the tread afforded by the fine spacing of the incisions.

References Cited in the le of this patent UNITED STATES PATENTS 2,094,636 Bun oct. 5, 1937 2,186,180 Sloman Ian. 9, 1940 2,261,025 Havens oct. 2s, 1941 2,302,027 Havens Nov. l, 1942 FOREIGN PATENTS 522,188 Great Britain June 11, 1940 809,470

France Mar. 3, 1937 v 

